Studies of the brains of patients with senile dementia have shown a decrease in cholinergic enzymes and thus presumably decreased cholinergic function in the cortex. Cholinergic receptors appear to be normal in amount. On this basis, increasing cholinergic activity in senile dementia might prove therapeutic. On this basis two parallel studies are proposed. The first is a double-blind 12-week study of oral lecithin in volunteer outpatients with senile organic brain states of mild to moderate degree. The second study will involve hospitalized patients with clear senile dementia. These patients will receive single intravenous doses of physostigmine, a drug which blocks acetylcholine destruction and arecoline, a presumed cholinergic agonist as well as a control infusion of saline. The short term effects of these cholinergic drugs on memory and EEG will be used to predict response to an open 6-month trial of lecithin in these patients.